This invention relates to semiconductor radiation detectors and, more particularly, to a new and improved semiconductor radiation detector.
As one type semiconductor radiation detector, our copending U.S. patent application Ser. No. 613,890 filed May 24, 1984 U.S. Pat. No. 4,692,782, proposed a detector which comprises a silicon crystal substrate, a hydrogenated undoped amorphous silicon film deposited on the substrate, and metal electrodes provided on the substrate and the amorphous silicon film. When a reverse bias voltage is applied between the electrodes, a high energy barrier is produced at the heterojunction to enlarge the depletion layer. More radiation arriving at the depletion layer is therefore captured and then detected.
The resistivity of hydrogenated undoped amorphous silicon is high, i.e., on the order of 10.sup.11 to 10.sup.12 .OMEGA.-cm. In addition, since the mobility band gap is inherent in the hydrogenated undoped amorphous silicon, the magnitude of the energy barrier at the heterojunction between the single crystal silicon and the hydrogenated undoped amorphous silicon is substantially fixed.
As a result, there is a limit in the reduction of a reverse leakage current which can be accomplished by that arrangement. Therefore, the depletion layer is not enlarged to a very great extent with the result that the most satisfactory radiation detecting efficiency is not obtained.
Accordingly, it is an object of the present invention to provide a semiconductor radiation detector having reduced reverse leakage current and improved radiation detecting efficiency.